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A "Hello, World!" message being displayed through long-exposure light painting with a moving strip of LED lights

A "Hello, World!" program generally is a computer program that outputs or displays the message "Hello, World!". Such a program is very simple in most programming languages, and is often used to illustrate the basic syntax of a programming language. It is often the first program written by people learning to code.[1][2]

Contents

PurposeEdit

A "Hello, World!" program is traditionally used to introduce novice programmers to a programming language.

"Hello, World!" is also traditionally used in a sanity test to make sure that a computer language is correctly installed, and that the operator understands how to use it.

HistoryEdit

 
"Hello, World!" program by Brian Kernighan (1978)

While small test programs have existed since the development of programmable computers, the tradition of using the phrase "Hello, World!" as a test message was influenced by an example program in the seminal 1978 book The C Programming Language.[3] The example program in that book prints "hello, world", and was inherited from a 1974 Bell Laboratories internal memorandum by Brian Kernighan, Programming in C: A Tutorial:[4]

main( ) {
        printf("hello, world\n");
}

The C language version was preceded by Kernighan's own 1972 A Tutorial Introduction to the Language B,[5] where the first known version of the program is found in an example used to illustrate external variables:

main( ) {
    extern a, b, c;
    putchar(a); putchar(b); putchar(c); putchar('!*n');
}
 
a 'hell';
b 'o, w';
c 'orld';

The program prints hello, world! on the terminal, including a newline character. The phrase is divided into multiple variables because in B, a character constant is limited to four ASCII characters. The previous example in the tutorial printed hi! on the terminal, and the phrase hello, world! was introduced as a slightly longer greeting that required several character constants for its expression.

The Jargon File claims that hello, world originated instead with BCPL (1967).[6][unreliable source?] This claim is supported by the archived notes of the inventors of BCPL, Prof. Brian Kernighan at Princeton and Martin Richards at Cambridge.[citation needed]

For modern languages, hello, world programs vary in sophistication. For example, the Go programming language introduced a multilingual program,[7] Sun demonstrated a Java hello, world based on scalable vector graphics,[8] and the XL programming language features a spinning Earth hello, world using 3D graphics.[9] While some languages such as Perl, Python or Ruby may need only a single statement to print "hello, world", a low-level assembly language may require dozens of commands. Mark Guzdial and Elliot Soloway have suggested that the "hello, world" test message may be outdated now that graphics and sound can be manipulated as easily as text.[10]

VariationsEdit

 
A "Hello, world!" program running on Sony's PlayStation Portable as a proof of concept.

The phrase has been used in various deviations in punctuation and casing, such as the presence of the comma and exclamation mark, and the capitalization of the leading H and W. Some devices limit the format to specific variations, such as all-capitalized versions on systems that support only capital letters, while some esoteric programming languages may have to print a slightly modified string. For example, the first non-trivial Malbolge program printed "HEllO WORld", this having been determined to be good enough.[11]

Variations in spirit exist as well. Functional programming languages, such as Lisp, ML and Haskell, tend to substitute a factorial program for Hello, World, as functional programming emphasizes recursive techniques, whereas the original examples emphasize I/O, which violates the spirit of pure functional programming by producing side effects. Languages otherwise capable of Hello, World (Assembly, C, VHDL) may also be used in embedded systems, where text output is either difficult (requiring additional components or communication with another computer) or nonexistent. For devices such as microcontrollers, field-programmable gate arrays, and CPLD's, "Hello, World" may thus be substituted with a blinking LED, which demonstrates timing and interaction between components.[12][13][14][15][16]

The Debian and Ubuntu Linux distributions provide the "hello, world" program through the software packaging system. It serves as a sanity check and a simple example to newcomers of installing a package. For developers, it provides an example of creating a .deb package, either traditionally or using debhelper, and the version of hello used, GNU Hello, serves as an example of writing a GNU program.[17]

Time to Hello WorldEdit

Time to "Hello World" (TTHW) is a metric for the time to author a "Hello World" program in a given programming language and run it.[18]

See alsoEdit

ReferencesEdit

  1. ^ James A Langbridge. "Professional Embedded ARM Development".
  2. ^ "sinobitorg/hardware". GitHub.
  3. ^ Kernighan, Brian W.; Ritchie, Dennis M. (1978). The C Programming Language (1st ed.). Englewood Cliffs, NJ: Prentice Hall. ISBN 0-13-110163-3.
  4. ^ Kernighan, Brian (1974). "Programming in C: A Tutorial" (PDF). Bell Labs. Retrieved 9 January 2019.
  5. ^ "The Programming Language B".
  6. ^ BCPL, Jargon File
  7. ^ A Tutorial for the Go Programming Language. Archived July 26, 2010, at the Wayback Machine The Go Programming Language. Retrieved July 26, 2011.
  8. ^ Jolif, Christophe (January 2003). "Bringing SVG Power to Java Applications". Sun Developer Network.
  9. ^ de Dinechin, Christophe (July 24, 2010). "Hello world!". Grenouille Bouillie.
  10. ^ "Teaching the Nintendo Generation to Program" (PDF). bfoit.org. Archived from the original (PDF) on 2016-05-05. Retrieved 2015-12-27. Cite uses deprecated parameter |dead-url= (help)
  11. ^ "Malbolge". Esolang. esolangs-wiki. Retrieved 28 October 2016.
  12. ^ Silva, Mike (11 September 2013). "Introduction to Microcontrollers - Hello World". EmbeddedRelated.com. Retrieved 19 May 2015.
  13. ^ George, Ligo. "Blinking LED using Atmega32 Microcontroller and Atmel Studio". electroSome. Retrieved 19 May 2015.
  14. ^ PT, Ranjeeth. "2. AVR Microcontrollers in Linux HOWTO". The Linux Documentation Project. Retrieved 19 May 2015.
  15. ^ Andersson, Sven-Åke (2 April 2012). "3.2 The first Altera FPGA design". RTE. Realtime Embedded AB. Archived from the original on 21 May 2015. Retrieved 19 May 2015. Cite uses deprecated parameter |dead-url= (help)
  16. ^ Fabio, Adam (6 April 2014). "CPLD Tutorial: Learn programmable logic the easy way". Hackaday. Retrieved 19 May 2015.
  17. ^ "Hello - GNU Project - Free Software Foundation". gnu.org. GNU Project. Archived from the original on 29 May 2014. Retrieved 7 July 2017. Cite uses deprecated parameter |deadurl= (help)
  18. ^ DuVander, Αdamd (31 July 2012). "Six Ways to Accelerate Time to First "Hello World"". ProgrammableWeb. Archived from the original on 30 June 2019. Retrieved 7 September 2018.

External linksEdit